about "insert into table with IF NOT EXISTS" error

[tom]

Hi:

  I setup one node cassandra server, and using node.js driver cql to query
db.

  But, when insert into table with "IF NOT EXISTS" statement, it report
error as below:

:ResponseError: Cannot achieve consistency level QUORUM

And, I try set nodejs cql query with consistency to ONE, still see that
error.

If I remove  "IF NOT EXISTS" from cql, insert passed.

 Please advice. thx.

best regards
  Tom